The invention relates generally to containers for handling, transporting and storing electronic components and more particularly, to containers which protect the contents against damaging electrostatic discharges.
Electronic components are typically transported from place to place and stored in some type of shipping container specifically designed for protection. Due to the increase usage of electrostatic sensitive electronic components, many shipping containers have been designed to include an electrostatic protection means. Components such as Metal Oxide Semi-conductors (MOS), field effect transistor silicon chips, small cross-sectional area semi-conductor junctions, piezoelectric crystals, and other such devices are relatively sensitive to electrostatic discharges. Thus, when handling or storing such components, an electrostatic protection means is typically used.
Some electrostatic protection means use a continuous conductive enclosure about the component thereby establishing an equi-potential surface and preventing the accumulation of externally generated electric charge inside the enclosure. In some cases, a means for interconnecting any charge residing on the enclosure with a dissipation means is used. An example is the carbon impregnated plastic bag. Such bags are used to surround the protected component and result in a conductive enclosure about the component. Electrostatic charge built up on the bag is dissipated by connecting the bag to a suitable ground or by bleeding it off into the atmosphere. However, these plastic bags are not rigid enough to provide a structure which will support stacking many such enclosed components on top of one another. Another enclosure is used in which the plastic bag is placed. Another consideration with this technique is the difficulty in performing inventory control. The identification material and other documents associated with the contents of the bag are usually placed in a separate pouch which is placed in the bottom of the container and must be removed by hand to inspect.
Other precautions used to protect sensitive electronic components include enclosing the sensitive component in a "bubble-wrap" which is partially electrically conductive, the use of temporary shorting devices during shipping and storage, the use of built-in protection devices such as zener diodes, and other techniques. While the above techniques are generally useful, in some cases further protection is ncessary.
A technique which provides further protection comprises a box-like, rigid, container which is coated with an anti-static material. One embodiment is the use of a clear plastic which is treated with a topical anti-static film. The sensitive component is secured inside the box and the box is closed thus forming a partially electrically conductive enclosure about the component. A conductor of some type may be connected to the box to provide a path to ground potential. The box thus forms an equi-potential surface to protect the contents from external electrostatic influences. In some cases, a partially electrically conductive, pliable, elastomeric, plastic foam is used inside the container to secure the sensitive component in position. The foam provides an electrical path from the sensitive component to the outer enclosure. Thus, charges accumulating on the sensitive component will be conducted away to the equi-potential surface and will be conducted to ground. Since they are rigid, these containers permit storage by stacking. However, it has been found that many anti-static coating materials are not always reliable for dissipating large charges. It has also been found that some liquids used to treat the plastic wear off. Thus the container must be tested routinely or discarded after a certain time. Also, this prior technique has been relatively expensive.
A technique found to be superior to the foregoing is the use of a partially electrically conductive plastic material molded into a box-like shape to hold the sensitive component. The plastic material forms the equi-potential surface around the component protecting it from external electrostatic influences. Such containers are rigid enough to be stacked and to protect the enclosed component from physical shocks. As in other techniques, a partially electrically conductive, elastomeric, plastic foam is used inside the container to secure the contents.
However, none of the above techniques have combined in one container features for protecting sensitive electronic components from electrostatic discharges during handling, transporting, and storing, while providing a container adapted for efficient inventory control. In many prior techniques, the accompanying documents are placed inside the container with the sensitive component. To review the documents, the container must be opened which breaks the protective surface surrounding the component and subjects it to possible electrostatic discharges due to this handling. A container that is static protective, presents certain information about its contents and allows access to accompanying documents without requiring that the container be opened, and which is easily inspected to assure that contents exist would be a valuable addition to the art.